Cleaning of water filtration membranes
Methods for cleaning water filtration membranes by treatment with a DNase containing cleaning composition. Optionally the composition also comprises a biocidal and/or other enzymes such as proteases. The DNAse may be derived from Aspergillus oryzae or from Bacillus licheniformis.
1. A method for cleaning a water filtration membrane, wherein the water filtration membrane comprises a biofilm, the method comprising
i) contacting the membrane with a liquid cleaning composition comprising a DNase and one or more non-DNase enzymes selected from arabinose, carbohydrase, cellulase, cutinase, galactanase, lipase, mannanase, oxidoreductase, pectinase, pectate lyase, perhydrolase, protease and xylanase; or
ii) contacting the membrane with a liquid cleaning composition comprising a DNase, and separately contacting the membrane with one or more non-DNase enzymes selected from amylase, arabinose, carbohydrase, cellulase, cutinase, galactanase, lipase, mannanase, oxidoreductase, pectinase, pectate lyase, perhydrolase, protease and xylanase.
2. The method of claim 1 , wherein the cleaning process is Cleaning-In-Place (CIP) or Cleaning-Out-of-Place (COP).
3. The method of claim 1 , wherein the water flow rate through the membrane (flux) is improved.
4. The method of claim 1 , which is preceded or followed by contacting the membrane with a biocidal composition.
5. The method of claim 1 , wherein the biofilm comprises one or more bacteria selected from the group consisting of Acinetobacter, Bacillus, Comamonas, Escherichia, Pseudomonas , and Sphingomonas species.
6. The method of claim 1 , wherein the biofilm comprises one or more bacteria selected from the group consisting of Acinetobacter calcoaceticus, Bacillus amyloliquefaciens SC100, Bacillus amyloliquefaciens SC168, Comamonas denitrificans, Escherichia coli K-12, Pseudomonas aeruginosa , and Sphingomonas mucosissima.
7. The method of claim 1 , wherein the pH of the cleaning composition is 6-9.
8. The method of claim 1 , wherein the membrane is contacted with the cleaning composition at a temperature between 30-100° C.
9. The method of claim 1 , wherein the DNase is an Aspergillus oryzae DNase or a derivative thereof.
10. The method of claim 1 , wherein the DNase is a polypeptide having DNase activity, which comprises or consists of an amino acid sequence having at least 80% sequence identity to the amino acid sequence shown as SEQ ID NO: 1.
11. The method of claim 1 , wherein the DNase is a polypeptide having DNase activity, which comprises or consists of the amino acid sequence shown as SEQ ID NO: 1.
12. The method of claim 1 , wherein the DNase is a Bacillus licheniformis DNase or a derivative thereof.
13. The method of claim 1 , wherein the DNase is a polypeptide having DNase activity, which comprises or consists of an amino acid sequence having at least 80% sequence identity to the amino acid sequence shown as SEQ ID NO: 2.
14. The method of claim 1 , wherein the biofilm comprises Pseudomonas aeruginosa.
15. The method of claim 1 , wherein the pH of the cleaning composition is about neutral.
16. The method of claim 1 , wherein the membrane is contacted with the cleaning composition at a temperature between 50-80° C.